It is known to provide non-circular screen wiping through a crank and crank arm system defining a deformable quadrilateral, in the manner that is best disclosed in French published patent specification FR 1 546 319A. In that case, the crank defines one of the sides of the deformable quadrilateral, while the crank arm which is articulated to the crank is defined by a part of a screen wiper arm which carries a wiper blade.
In the arrangements already known from the prior art, the crank and the crank arm are coupled together through the pivot member, which defines the above mentioned axis of rotation and which has a head, a first cylindrical portion, and a second cylindrical portion which is of smaller diameter than the first cylindrical portion, with the head and the two cylindrical portions being coaxial with each other.
It is known to connect the second cylindrical portion of the pivot member to the crank arm by riveting the end of that cylindrical portion. However, the present Applicant has found that such a means of connection has various drawbacks.
Firstly, the axial stresses exerted on the pivot member during the riveting operation cause the crank arm to be weakened by upsetting the terminal end of the second cylindrical portion of the pivot member into the material that constitutes the crank arm itself.
In addition, since both the crank arm and the crank are made of a soft material, and in particular a Zamak based material, while the pivot member itself is of a hard material, it has been found that the crank undergoes considerable wear in contact with the pivot member. This wear reduces the useful life of the screen wiping apparatus, and/or leads to deterioration in the mechanical qualities of the articulation.